High pressure dies



May 31, 1960 w. B. WILSON 2,938,998

HIGH PRESSURE DIES Filed April 3, 1959 r INVENTOR. Mendel! ,8. 11117501:

and heating a specimen.

Unite HIGH PRESSURE DlES Filed Apr. 3, 1959, 591'. No. 804,057

7 Claims. (31. 219-149 This invention relates to an apparatus forcompressing More specifically, the invention relates to an arrangementof cooperating pressure dies and a heater used therewith for acting oncertain materials being studied for the effects that high pressures andelevated temperatures have upon them.

It has been found desirable to study the eifects of high pressures andelevated temperatures on certain materials such as bismuth, urania (Uyttria (Y O and thoria (ThO particularly when the high pressures andelevated temperatures are maintained for relatively long times. Onedrawback with known apparatuses for these purposes is that it has beenimpossible to subject a material being studied to very high temperatureand very high pressure at the same time, though these conditions mightbe obtained separately. Another drawback has been that die materialshard or inelastic enough to obtain high pressures would break withcertain stresses.

An object of the present invention is to provide an apparatus that willsubject a specimen to high pressure and elevated temperaturesimultaneously. In the present apparatus a heater is contained within adie chamber and the die parts are protected from the weakening effectsof the elevated temperatures to which the material under study issubjected.

A further object is to provide support and protection for hard pressuredies which prevent these dies from being broken without interfering withtheir ability to produce high pressure through reduction in size of thedie space.

Other objects will appear from the description and the drawings inwhich:

Fig. 1 is a sectional view of the novel apparatus of the presentinvention;

Fig.2 is a sectional view, similar to Fig. 1, of the portion of theapparatus contained in the circle 2 in Fig. 1;

Fig. 3 is a diagrammatic view of the portion of the apparatus in Fig. 2,showing volume changes produced by the apparatus; and

Fig. 4 is a diagrammatic view showing the portion contained in thecircle 4 in Fig. 3.

As shown in Figs. 1 and 2, the apparatus of the present inventioncomprises upper and lower male dies 20 and 21, a female die 22 receivingthe male dies, an electrically insulating layer 23 between the dies 20and 22, an electrically nonconducting thermal insulator 24 in the diespace, a resistance-heater tube 25 within the thermal insulator 24, andthermally-insulating plugs 26 fitting within the ends of the tube 25.The tube 25 and plugs 26 enclose a sample or specimen 27 to be pressedand heated.

The heater tube 25, which is formed of graphite, or a metal such astungsten, nickel or platinum, is needed if the specimen 27 is anonconductor or poor conductor such as uram'a or yttria or is aconductor only at high temperatures such as thoria. When a graphiteheater is used it is necessary to line the heater with a material suchas beryllia, BeO, to allow study of oxide systems.

atent O "we 2938998 Patented May 31, 1960 If this is not done, thegraphite will react with the oxide sample. The beryllia lining 27aterminates short of the ends of the heater tube 25, so that the plugs 26will contact the interior of the heater tube at or near its ends. If thespecimen 27 is a good conductor such as bismuth, the specimenconstitutes its own electrical-resistance heater, and neither tube 25nor plugs 26 are needed. The thermal insulator 24 is formed of silverchloride or unfired pyrophyllite such as Al O .4 SiO .H O or unfiredsteatite such as 3 MgO.4 SiO H O. Plugs 26 may be formed, for example,of a thermallyinsulating material such as nickel, pyrophyllite orsteatite.

The male dies 20 and 21 are formed of a very hard material such astungsten carbide cemented by cobalt, for example, 6 w/o. The female die22 is formed of a somewhat softer material such as 4340 or 4140 SAEsteel having a Rockwell hardness of 60-62. The male dies 20 and 21 havefrustoconical portions 28 which fit frustoeonical recesses 29 formed inthe female die 22. The recesses 29 are axially aligned and are connectedby a circular cylindrical recess 30 aligned therewith, in

which the thermal insulator 24 fits.

The male dies 20 and 21 are mounted, respectively, in a head 31 and abase 32, which may be of steel, by means of backing members 33 andsleeves 34, which are press-fitted or shrink-fitted on the male dies andare formed of 4340 or 4140 SAE steel having a Rockwell hardness of 6062. The backing members 33 have a hardness comparable with that of themale dies 20 and 21 and so may be formed of tungsten carbide cementedwith 6 w/o cobalt. The backing members are of appreciably greaterdiameter than the male dies 20 and 21 and so distribute the end thrustof the dies 20 and 21 over wider areas of the head 31 and base 32, withless tendency of these parts to distort because of being softer than thebacking members 33. The sleeves 34, which are threaded in the head 31and base 32 and carry the backing members 33 and dies 20 and 21, providecircumferential support to the dies 20 and 21 and so lessen theirtendency to fracture under shear.

The female die 22, which is slightly smaller in outer diameter at itsbottom than at its top, is pressed in an inner binding ring 35, which issmaller in inner and outer diameters at its bottom than its top. Theinner binding ring 35, whch may be formed of 4340 or 4140 SAE steelhaving a Rockwell hardness of 48-52, is pressed in an outer binding ring36, which may be formed of the same steel having a Rockwell hardness of32-36. The ring 36 is smaller in inner diameter at its bottom than itstop and is pressed in a safety ring 37, which may be formed of mildsteel.

An annular shield 38 rests on the ring 36 and protects against flyingpieces that would result if the upper male die 20 fractured. An annularwall 39 is provided to contain cooling water around the lower male die21 and its sleeve 34. The wall 39 carries in grooves in its upper andlower edges, O-ring seals 40, which are pressed against the outerbinding ring 36 and the base 3'2. The wall 39 and the water containedtherein will protect against possible shattering of the lower male die21.

The insulating layer 23 between the upper male die 20 and the female die22 is preferably of Fe O in the form of rouge painted on both thetrustoconical portion 28 of the upper die 20 and the upper frustoconicalrecess in the female die 22. The layer 23 is thick enough to enablethermocouples to be brought out of the sample 27 through the layer. Thefrictional properties of Fe O of which the layer is formed, prevent thethermal insulator 24 from being squeezed out between the upper male die20 and the female die 22. The frustoconical portion 28 of the lower maledie 21 is lubricated so spasms that, as the male dies and 21 move towardone another, the female die 22 is expanded.

At the start of the operation, when upper male die 20 is elevated fromthe position of Fig. l, the thermal insulator 24 is fitted into thecylindrical recess 30 in the female die 22, the heater tube 25 isinserted in the insulator 24, the lower plug 26 is put in the heatertube 25, the specimen 27 is inserted therein, and the upper plug 26 isplaced in the tube 25 on top of the specimen 27. The preliminaryover-all height of this assembly of insulator 24, heater tube 25, endplugs 26, and specimen 27 may be a little greater than the length of thecylindrical recess 30, so that the specimen 27 may be preliminarilycompressed when the frustoconical portion 28 of the upper die is broughtinto engagement with the upper frustoconical recess 29 of the female die22.

. Additional downward force is applied to the upper male die 20 to moveit closer to the lower male die 21. This is possible, because the femaledie 22, being of steel, has appreciable elasticity and can expand. It isnecessary to relate the height of the cylindrical recess 30, or theassembly of insulator 24-, heater 25, plugs 26, and specimen, the radiusthereof, and the angle of the frustoconical die portions 28 to oneanother in such a way that the decrease in volume due to contraction inheight is greater than the increase in volume due to increase in radius.Reference is made to Fig. 3, wherein the fulllines show the diepositions before the female die 22 is expanded, the dotted-lines showthe die positions after the female die is expanded, and the hatchedareas show the volume changes. Thus, the volume decrease due to heightcontraction is ZAh'yr and the volume increasedue to radius expansion isapproximately Z'yrhAr. Since the volume decrease must be greater thanthe volume increase for the sake of pressure increase, 2Ah'yr Z'yrhAr orr/h Ar/Ah. Since, as seen from Fig. 4, the relation of the increase inradius to the decrease in height is related to the angle thefrustoconical portions 28 make with their axes, as expressed by theequation Ar/Ah: tan 0, by substitution it is seen that it is necessaryfor r/h tan 6.

On this basis, satisfactory results were obtained with r=.25", 11:25,"and 6:35". The preliminary height of the assembly of insulator 24,heater tube 25, plugs 26, and specimen 27 was .31". As the male die 20is pushed into recesses 29 in female die 22, the excess height of thesample is crushed into the die bore which serves to compact the sampleand eliminate voids.

The size of the heater tube 25 may be varied from to over For example, athin-walled platinum tube A3" in diameter may be used as may a graphitetube varying from /s" to The wall thickness of the heater tube is notimportant since this aifects only the power required to obtain a giventemperature.

Electric current is supplied to the heater tube 25 through the male dies20 and 21 and is forced to go through the heater-tube 25 because of theinsulating layer 23 between the upper male die 20 and the female die 22.Since the heater tube 25 lies within the thermal insulator 24, thefemale die 22 is thermally shielded and is not weakened by heating. Theplugs 26 prevent the specimen 27 while being compressed from flashingout over either end of the heater tube 25 and the male dies 20 and 21.Pressures in excess of 110,000 atm. have been obtained with an appliedforce of 225 tons. The theoretical maximum is about 200,000 atmospheres.

With the die arrangement of the present invention, the advantage of thedie space of right-cylindrical shape is kept, namely, the ability toreduce volume and thus increase pressure. Yet the dies 20 and 21, whichare extremely hard and likely to fracture in shear, are supported by thedie 22 so as to be protected from fracture. Likewise the die 22 issupported against fracture by binding ring 35. The frustoconicalportions 28 of the dies 20 and 21 and the frustoconical recesses 29 inthe 4 die 22 receiving them provide the dies 20 and 21 with supportagainst fracture while permitting them to reduce the height of the diespace afforded by the recess 30 in the die 22. Proper proportioniing ofparts makes reduction of volume possible through height reduction inspite of radius increase of the recess 30 due to supporting the dies 20and 21 against fracture while they move toward one another. Thefrustoconical shaping of the die parts recesses being shaped to receivethe frustoconical male dies, an annular cylindrical thermal insulatorfitting within the cylindrical middle portion of the opening in thefemale die, an electrically conducting tube fitting within the thermalinsulator and having its ends in electrical contact with the male dies,and short thermally insulating plugs fitting within the ends of the tubeso as to be adapted to cooperate with the tube in containing thespecimen within the tube and between the end plugs, one male die beingelectrically insulated from the female die by a layer of Fe O rougebetween said one male die and the frustoconical recess in the female diemating therewith.

2. The apparatus specified in claim 1, the female die being of steelhaving a Rockwell hardness of 60-62, the male dies having 6% cobalt, theelectrically conducting tube being of platinum, the thermal insulatorbeing of pyrophyllite or steatite, the plugs in the tube being ofnickel.

3. Apparatus for exerting very high pressures on a specimen andsimultaneously heating it, said apparatus comprising a plurality ofcooperating male and female dies of electrically conducting materialfitted together to enclose a cylindrical space, an annular cylindricalthermal insulator occupying the radially outermost portion of the space,an electrically conducting tube fitting within the thermal insulator andhaving its ends in electrical contact with the male dies, and shortthermallyinsulating plugs fitting Within the ends of the tube so as tobe adapted to cooperate with the tube in containing the specimen withinthe tube and between the end plugs, one die being electrically insulatedfrom another of the contacting it by a layer of Fe O applied betweenthese two dies.

4. The apparatus of claim 3, the electrically conducting tube being ofgraphite having a beryllia lining, and the thermal insulator and theplugs being of pyrophyllite or steatite.

5. The apparatus of claim 3, the electrically conducting tube being ofplatinum, the thermal insulator being of pyrophyllite or steatite, theplugs in the tube being of nickel. v

6. Apparatus for exerting very high pressures on a specimen, comprisingmale dies of tungsten carbide having frustoconical surfaces, and a steelfemale die having aligned frustoconical recesses joined by a circularcylindrical recess, the frustoconical recesses being shaped to engagethe frustoconical surfaces of the male dies, the ratio of the height ofthe cylindrical recess to its radius being greater than the tangent ofthe angle made by the frustoconical surface of each rnale die with itsaxis.

7. Apparatus for exerting very high pressures on a specimen andsimultaneously heating it, said apparatus comprising a plurality ofcooperating male and female dies of electrically conducting materialfitted together to enclose a space, an annular thermal insulatoroccupying the radially outermost portion of the space, and an 5electrically conducting tube fitting within the thermal insulator andhaving its ends in electrical contact with the male dies, the tube beingadapted to contain the specimen, one die being electrically insulatedfrom another of the dies contacting it by a layer of F6 0 between thesetwo dies.

References Cited in the file of this patent UNITED STATES PATENTS

